Although ozone, which has an oxidative effect, a sterilizing effect, a deodorant effect, and the like, is expected for use in various fields, due to the form of gas, ozone lacks versatility when directly used. Accordingly, in order to effectively utilize ozone, for example, ozone has to be dissolved in water to be used as an ozone water. However, ozone has drawbacks of essentially low solubility in water and a very short half-life in the state of being dissolved in water. For this reason, ozone is currently used after ozone gas is dissolved in water at the site of use by a method such as bubbling. Such a method, however, has a problem of a production apparatus of ozone water required to be brought to the site of ozone use, and problems of the cost and countermeasures against exhaust ozone. Accordingly, the practical use of ozone has not become common yet.
Thus, the present inventor proposes, in Patent Document 1, as a method for drastically improving low storability of ozone water which is a drawback thereof, a technique for securing long-term storability while maintaining the effects of ozone, by utilizing ozone bubbles of nano-sizes (ozone nanobubbles). However, further enhancement is demanded in storage stability of ozone water at the site of ozone use.